Lab methods for the analysis of microbiological quality of milk and food

Introduction

There are several microbiological organisms associated with food and milk products like bacteria, yeast, citric acid-producing fungi which help in the process of fermentation that changes the form of dairy products like cheese and yoghourt; it also helps in the process of production of wine, bread, and other bakery products. Microbiological organisms present in food and dairy products have different health benefits as well and they are analysed by several lab methods. In this study, several lab methods for the analysis of the microbiological quality of milk and food products will be elaborated.

Microbiological quality of milk

There are several microbiological organisms present in the milk that help in the process of formation of several dairy products by the process of fermentation and acidification; These processes take place during handling and storage of milk, microbes associated with milk in the formation of several milk products

Lactobacillus present in the milk helps in the process of the souring of the milk enhancing their citric properties, which further helps in the formation of curd. The sour taste is formed due to the lactobacillus converting the lactose of the milk to lactic acid
In the formation of yoghourt, several bacteria are used like streptococcus thermophilus, Lactobacillus acidophilus that are probiotic and they come with several health benefits as well.
Cheese is one of the most popular household products. The process of fermentation of milk forms cheese. The presence of bacteria like Lactobacillus lactis and Streptococcus thermophilus helps in the process of coagulation in turn acidification of milk for the production of cheese.
Kefir is one mild milk beverage that is mostly found in Eastern Europe. This alcoholic beverage is formed in the presence of kefir grains, which contain microbes like lactobacillus acidophilus, and Lactobacillus kefir helps in the production of this beverage by acidification.
Kumis is one such beverage similar to kefir, which is made using the Lactobacillus rhamnosus, and Lactobacillus bulgaricus which causes the acidification of the milk.

Tests for microbiological quality of milk

There are several tests associated with the lab that help in the process of detection of the presence of bacteria level and effect on milk products.

Phosphatase and methylene blue reduction lab tests – These tests are conducted for the detection of microbes present in the pasteurised milk, The standard plate count as derived helps in detecting the presence of bacteria in a certain amount of milk, these tests are used for grading the milk.
Coliform plate count test – This test is used to determine the total number of coliforms present in milk, detecting the total amount of microbes present in pasteurised milk.
Somatic cell count test – This test is conducted in the lab to take note of the presence of any infection in milk as derived from the cow. A high SCC count would indicate the presence of infection in the cow’s udder in turn the milk.

Milk product testing and quality control

Clot on boiling testing – this test is used to detect the acidity of the milk by boiling a spoonful of milk in the test tube, the presence of coagulation or clotting would indicate excessive acidity in the milk.
Alcohol test – Alcohol test is a simple test conducted in the lab, this test is conducted by adding milk in a 68% ethanol solution. Any sign of coagulation would indicate the presence of instability of proteins in the milk

Conclusion

The study above reflects the presence of microbes and microbiological quality in milk, dietary products with the presence of microbes in high content might cause health issues however in a balanced amount will prove to be beneficial for the health by dissolving and helping in the process of digestion of protein complexes present in food products. Variants of microbes like lactobacillus and streptococcus help in the process of acidification and thus help in the formation of several milk products. Presence of these helpful microbes although aid in our health however quality of the milk should be monitored thoroughly to check the spread of diseases.